The present invention relates to an apparatus for bending a cutting blade, and more particularly to an apparatus for mechanically bending a cutting blade into a predetermined profile by the use of rotating bending members.
The most conventional and well-known traditional method to bend a cutting blade may be the skill of manually punching the blade for imparting appropriate curves thereto. The advent of automatic processing has also influenced on the fields to which the present invention pertains so that various types of automatic bending machines have been developed, the typical one being shown in FIG. 12.
As it can be seen from FIG. 12, GB 2,116,086 discloses an apparatus in which a rotating pin 70, which is placed in front of a guide 64, folds or bends a rule whose advance forward is guided by the guide 64, the pin 70 being eccentrically planted in a spindle 68. Rotating movement of the spindle 68 makes the pin 70 rotate or revolve around its center until the pin 70 contacts and exerts lateral force on the rule, and such inflicted force is also focused on the head part of the guide 64. Accordingly, the rule portion between the pin 70 and the head of the guide 64 finally bends, its bending angle naturally depending upon the net rotated angle of the pin 70.
Another prior art is disclosed in U.S. Pat. No. 5,870,919, which is substantially identical to the above apparatus, the differences being that it adopts two folders and two rotary bodies that act as spindles. According to this invention, one folder assumes bend of, for example, left side of the rule, and the other right side of the rule.
There have been also attempts for bending various cutting blades having different width with a single bending machine. For instance the apparatus of Japanese Unexamined Patent Publication No. Hei10-286,625 places on a platform a plurality of folders with different width, and, in the bending processing, selects a suitable one based upon the width of the cutting blade to be bent which affords to provide the most proper bending force. However, despite of the merit of wider applications, this invention does not consider the most important physical property of the cutting blade likewise other prior arts.
That is, as illustrated in FIG. 9, a conventional cutting blade A consists of a body portion A' and a blade portion A" formed upwards on the body portion A' to shape a triangle with a pointed acute tip or blade. In order to sustain persistent cutting ability, the blade portion A' that directly engages with a blank to be cut should be made to have higher rigidity, stiffness and toughness, so that the blade portion A' is subject to more intensive heat treatment compared to the body portion A'. Accordingly, the physical properties of these two portions are different from each other, which results in different behaviors under spring back. Once a cutting blade is bent, the blade portion A" having relatively higher elasticity due to intensive heat treatment, is subject to stronger spring back effects so that it shows more tendency of returning back to its original position. Its final horizontal bending angle becomes smaller than that of the body portion A'.
Practical problems arise from the fact that the spring back behavior of the blade portion A" is extended onto a considerable upper area of the body portion A', there being found many cases in which nearly half the upper area of the body portion A' shows the same behavior as that of the blade portion A". This is because a strong resilient force by spring back acting on the blade portion A" is also transferred to the upper body portion beyond a borderline between the two portions A', A". Further, high temperature effects at the blade portion A" under intensive heat treatment are also delivered to a considerable region of the body portion A' so that it cannot be avoided that the upper part shows stronger rigidity and resilience than the lower part of the body portion A'. Residual torsion and deformation are found in the thus formed cutting blade, and the final bending angle of the upper part of the cutting blade A including blade portion A' becomes smaller than that of the remaining lower part. One can easily find these drawbacks when making a minute and small cutting blade for fabricating complicated and small articles calling much demand nowadays.
Therefore, it is a primary object of the present invention an apparatus is provided for a cutting blade that can form an accurate vertical profile and a uniform bending angle without any deformation or torsion even under spring back phenomenon.
Next, the height of each cutting blade is different depending upon the blank to be cut, ranging from some millimeters to centimeters. It is natural that a folder cannot bend a taller cutting blade. To the contrary, using a folder much taller than a cutting blade entails a problem that strong and uniform lateral force is difficult to be exerted on all the contacting areas between the cutting blade and the folder, and to use a thick folder to solve this problem again gives rise problems of not providing minute and accurate bends.
An apparatus is provided for a cutting blade that can provide strong and uniform lateral force on the cutting blade without changing the entire apparatus.
The present invention basically includes a guide having a guide passage formed therein for transferring the cutting blade in a lengthwise direction, a first rotary body located at an upper position adjacently to a head of the guide, a second rotary body located at a lower position adjacently to the head of the guide and opposite to the above upper position, a first bending member supported by a hole formed on the first rotary body, a second bending member supported by a hole formed on the second rotary body, the second bending member being oppositely located to the first bending member in a substantial perpendicular direction to the above lengthwise direction (hereinafter referred to as "vertical direction" throughout the specification), a drive means for driving the first and second rotary bodies, and linear drive means for linearly moving the respective first and second bending members in a vertical direction.
According to the above features of the present invention, since it is possible to adjust relative positions of the first and the second bending members, independent forces can be applied to each upper and lower portions of the cutting blade, which forces are adjusted based upon predetermined sizes of the cutting blade such as height and thickness and in particular physical property thereof, thereby eliminating or minimizing drawbacks caused by spring back effects and forming the cutting blade into desirable precise profiles. It should be noted that prior arts have simply had a bending member rotate further than final bending angle to compensate for spring back, and never noticed that the upper portion and lower portion of the rule differently respond to this situation.
Further, the present invention is characterized in that the first bending member is spaced by a small distance from the second bending member towards the guide in a lengthwise direction. This can be done by either having the first rotary body and the first bending member supported thereby move towards the head of the guide by the use of a movable setting means for the first rotary body, or having the second rotary body and the second bending member supported thereby move towards opposite direction to the head of the guide by the use of a movable setting means for the second rotary body.
According to this feature of the present invention, when drive means rotate at a predetermined speed, the first rotary body which is set to be placed more closely to the drive means has more rotary number than the second rotary body, accordingly, net rotated angle of the first bending member becomes larger than that of the second bending member, leading to a larger curve or bending at the upper portion of the cutting blade. However, once the cutting blade is subject to spring back, as sprung back or withdrawn angle at the upper portion is larger than that at the lower portion, as is explained above, this completely absorbs the initial bending difference of the upper portion from the lower portion, and thus made cutting blade provides accurate vertical profiles and uniform horizontal bending angle without deformation or torsion.
Further, the present invention is characterized in that each movable setting means accommodating each first and the second rotary body is moved by a small distance in a lengthwise direction by the control of distance adjusting bolts affixed thereto.
Thus, it is possible to easily and minutely adjust the position of each rotary body held by the movable setting means by controlling the distance adjusting bolts.
Further, the present invention has the first rotary body and the second rotary body be connected to the drive means via belts.
Thus, if the rotary body moves towards or away from the head of the guide, the distance gap caused by movement of the rotary body can be completely absorbed by the resilient and elastic belt without affecting on tight and smooth power transmission from the drive means to the rotary body.
Further, the present invention is characterized in that the first rotary body and/or the second rotary body includes an upper radial portion which is directly connected to the drive means, a lower radial portion integrally formed with and protruding from the upper radial portion, and a bending member guide having the hole formed therein, and protruding outwards from the lower radial portion.
Further, the present invention is characterized in that the length of the first and second bending members engaging with the cutting blade can be adjusted in a vertical direction.
According to this feature of the present invention, especially when bending a short and thick cutting blade, it is possible to exert uniform and strong force on the cutting blade by adjusting the projected part of the bending members into the working region in a vertical direction, so more accurate bending can be effectively achieved.
Further, the present invention is characterized in that the bending member guide is exchangeable. The bending member guide is preferably fixed to a holder which is again fixed to the side or bottom portion of the second radial portion of the rotary body.
According to this feature of the present invention, it is possible to bend cutting blades of various height with a single apparatus by changing the bending member guide, requiring no alteration or change of the bending member as well as the entire machine. Thus, merits of high productivity and low cost are expected.